Natural circulation type cooling apparatus

ABSTRACT

According to one embodiment, a natural circulation type cooling apparatus includes a heat receiver with a heat receiving surface on which an exothermic body is mounted, and containing therein a coolant, a condenser on a horizontally lateral side of the heat receiver, a radiator on a horizontally lateral side of the heat receiver and on a vertically downward side of the condenser, a vapor conduit configured to feed vapor of the coolant to an inlet of the condenser, a condensed liquid conduit configured to feed a condensed coolant from an outlet of the condenser to an inlet of the heat receiver, a coolant conduit configured to feed the coolant to an inlet of the radiator, and a circulation conduit configured to feed the coolant from an outlet of the radiator to the inlet of the heat receiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2012-117812, filed May 23, 2012, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a cooling apparatusapplied with a natural circulation liquid cooling method, in which acoolant circulation pump for providing an external driving force is notused, and which cools an exothermic body such as a semiconductor devicethat is used in a power converter for a railway vehicle.

BACKGROUND

In general, a power converter for a railway vehicle comprises anexothermic body such as a semiconductor device, and a cooling apparatusfor cooling such an exothermic body. As a cooling method of alarge-capacity cooling apparatus, a boiling cooling method and a forcedcirculation liquid cooling method are applied. In a cooling apparatus towhich the former cooling method is applied, there are, because of thedevice structure, such restrictions on disposition that ahigh-temperature unit is disposed on a lower side and a low-temperatureunit is disposed on an upper side. In addition, it is the fact thatthere is an international trend toward complete disuse of a Freon-basedcoolant which is used for this cooling method. On the other hand, in acooling apparatus to which the latter cooling method is applied, thereare many structural elements which accompany the cooling system, such asa circulation pump, conduits, a fluid reservoir tank, a heat exchanger,etc., and there are demerits such as an increase in volume forinstallation and an increase in cost due to this.

In recent years, there has been proposed a technique for a coolingmethod, in which the demerits of both of the above-described coolingmethods are eliminated. In this technique, a coolant is naturallycirculated in the system. Specifically, buoyancy of boiling bubbles,which are generated by the exothermic body, such as a semiconductordevice, is used as a circulation driving force. According to thisnatural circulation cooling method, a passive cooling system, which usesno external driving force, can be constructed.

In a cooling apparatus using the above-described natural circulationcooling method, a heat exchanger for condensing a generated vapor isdisposed on an upper side of a heat receiver to which the exothermicbody is attached, and a radiator is disposed on a lateral side of theheat receiver. In the case of this structure, because of the positionalconfiguration within the power converter, there are cases where thedirection of disposition of the cooling apparatus is restricted due toproblems with the space occupied by the apparatus, the equipment size,and the mounting of the apparatus. Hence, the degree of freedom ofdesign of the entire apparatus system decreases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view which schematically illustrates a railway vehicleincluding a natural circulation type cooling apparatus according to afirst embodiment;

FIG. 2 is a plan view which schematically illustrates an underflow sideof the railway vehicle;

FIG. 3 is a front view which schematically illustrates the coolingapparatus according to the first embodiment;

FIG. 4 is a partially cutaway perspective view of a heat receiver of thecooling apparatus;

FIG. 5 is a cross-sectional view of the heat receiver, taken along lineA-A in FIG. 4;

FIG. 6 is a cross-sectional view of the heat receiver, taken along lineB-B in FIG. 4;

FIG. 7 is a front view which schematically illustrates a naturalcirculation type cooling apparatus according to a second embodiment;

FIG. 8 is a side view which schematically illustrates a naturalcirculation type cooling apparatus according to a third embodiment;

FIG. 9 is a cross-sectional view showing an internal structure in anupper part of a heat receiver of the cooling apparatus according to thethird embodiment;

FIG. 10 is a side view which schematically illustrates a naturalcirculation type cooling apparatus according to a fourth embodiment;

FIG. 11 is a side view which schematically illustrates a naturalcirculation type cooling apparatus according to a fifth embodiment;

FIG. 12 is a side view which schematically illustrates a naturalcirculation type cooling apparatus according to a sixth embodiment; and

FIG. 13 is a side view which schematically illustrates a naturalcirculation type cooling apparatus according to a seventh embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, anatural circulation type cooling apparatus comprises: a heat receivercomprising a heat receiving surface on which an exothermic body ismounted, and containing therein a coolant in a liquid phase; a condenserprovided on a horizontally lateral side of the heat receiver, andconfigured to condense a vapor which is generated by the heat receiver;a radiator disposed on a horizontally lateral side of the heat receiverand on a vertically downward side of the condenser, and configured tocool the coolant which is fed from the heat receiver and is heated; avapor conduit configured to feed the vapor of the coolant, which isgenerated by the heat receiver, to an inlet of the condenser; acondensed liquid conduit configured to feed the coolant, which iscondensed, from an outlet of the condenser to a coolant inlet of theheat receiver; a coolant conduit configured to feed the coolant, whichis heated in the heat receiver, to an inlet of the radiator; and acoolant circulation conduit configured to feed the coolant, which iscooled in the radiator, from an outlet of the radiator to the coolantinlet of the heat receiver.

First Embodiment

FIG. 1 and FIG. 2 are, respectively, a side view and a plan view whichschematically illustrate a railway vehicle including a naturalcirculation type cooling apparatus according to a first embodiment. Therailway vehicle comprises a truck 12 provided with wheels 14, and avehicle body 16 supported on the truck 12. A traction motor 18 ismounted on the truck 12 in the vicinity of the wheels 14. The tractionmotor 18 transmits a torque to the wheels 14 via a gear box and acoupling, which are not shown. The wheels 14 are placed on rails 13.Various devices including a power converter 20 are equipped under thefloor of the vehicle body 16. A natural circulation type coolingapparatus 10 according to the embodiment is configured, for example, asa cooling apparatus for cooling semiconductor devices (exothermic body)which constitute the power converter 20, and is disposed under the floorof the vehicle body 16.

FIG. 3 is a front view schematically showing the structure of theentirety of the cooling apparatus 10. FIG. 4, FIG. 5 and FIG. 6 are,respectively, a perspective view and cross-sectional views showing aheat receiver of the cooling apparatus 10. As shown in FIG. 1 to FIG. 3,the cooling apparatus 10 comprises a heat receiver 22 which coolssemiconductor devices by receiving heat from the semiconductor devices,a condenser 24, a radiator 26, and a plurality of conduits whichinterconnect these components. In the embodiment, the cooling apparatus10 further comprises an air blower 28.

The heat receiver 22 is provided, for example, within a housing 21 ofthe power converter 20, and is positioned in a substantially verticalplane. The condenser 24 and radiator 26 are arranged in the verticalplane common with the heat receiver 22, or in another vertical planeparallel to this vertical plane. The condenser 24 is provided on ahorizontally lateral side of the heat receiver 22. The radiator 26 isarranged on the horizontally lateral side of the heat receiver 22, andon a vertically downward side of the condenser 24. The air blower 28 isopposed to the rear side of the condenser 24 and radiator 26.

As shown in FIG. 3 to FIG. 6, the heat receiver 22 includes a containerbody 30 having an elongated rectangular box shape, and an uppercontainer 32 of a rectangular box shape, which covers an upper part ofthe container body 30 and forms a sub-flow passage which will bedescribed later. One or both of major surfaces of the container body 30constitute a heat receiving surface 30 a. A plurality of semiconductordevices 36, for example, two semiconductor devices 36, which areexothermic bodies, are mounted on the heat receiving surface 30 a. Thesemiconductor devices 36 constitute a part of the power converter 20.

The container body 30 is formed in a predetermined size in accordancewith the cooling capability of the cooling apparatus, and apredetermined amount of liquid-phase coolant 34 is sealed in thecontainer body 30. As the coolant 34, use is made of pure water, ahydrocarbon-based coolant, an ammonia aqueous solution, an antifreezeliquid (ethylene glycol aqueous solution, propylene glycol aqueoussolution, etc.), or a heat-accumulation microcapsule. In general, achemically stable coolant is used, and the coolant preferably hasthermophysical properties of high evaporation latent heat and thermalconductivity, and a low viscosity coefficient.

As the material for forming the heat receiving surface 30 a of the heatreceiver 22, aluminum or brass is used in accordance with the coolantthat is applied. In addition, it is possible to apply a material inwhich heat transfer is promoted by reforming the heat receiving surface30 a with an external physical treatment such as beam irradiation orflame spray coat shaping.

A plurality of partition plates 38 are provided in the container body 30of the heat receiver 22, so as to form desired flow passages orcontaining chambers. The partition plates 38 are arranged in thevertical direction within the container body 30, and at predeterminedintervals in the horizontal direction. Containing chambers 40 whichcontain the coolant 34, or passages, are formed between mutuallyneighboring partition plates 38 or between the partition plates and sidewalls of the container body 30. A lower end of each partition plate 38is slightly spaced apart from a bottom wall of the container body 30,and thereby the plural containing chambers 40 communicate with eachother in the lower part within the container body 30.

In addition, an upper end portion of each partition plate 38 extendsupward, beyond an upper opening 30 b of the container body 30, and islocated within the upper container 32. The upper end portions of thepartition plates 38 form baffle plates 42. The baffle plates 42 restrainthe coolant 34, which flows out of each containing chamber 40 of thecontainer body 30, from flowing into the neighboring containing chambers40. In the meantime, the structure of the baffle plate 42 is not limitedto the structure in which the baffle plate 42 is formed integral withthe partition plate 38. The baffle plate 42 may be configured such thata separately formed baffle plate is fixed to the partition plate 38.

By the upper container 32, a sub-flow passage 44 is formed around theupper opening 30 b of the container body 30. The coolant 34, which isheated and flows out of each containing chamber 40, flows into thesub-flow passage 44, and is fed to a coolant outlet (to be describedlater) through the sub-flow passage 44. The sub-flow passage 44 may beconfigured to be inclined at a desired angle to the coolant outlet side,so that the coolant may efficiently be fed to the coolant outlet.

A vapor exhaust port 46 is formed in a ceiling wall of the uppercontainer 32, and this vapor exhaust port 46 communicates with theplural containing chambers 40 via a space within the upper container 32.A coolant outlet 48 is formed in a side wall of the upper container 32,and this coolant outlet 48 communicates with the sub-flow passage 44. Acoolant inlet 50 is formed in a bottom wall of the container body 30,and this coolant inlet 50 communicates with the plural containingchambers 40.

As shown in FIG. 3, the condenser 24 includes a conduit 52 which extendsin a bellows shape and flows vapor, and a plurality of radiation fins 54which are disposed directly or indirectly on the periphery of theconduit 52. The conduit 52 includes an inlet 56 a which is located atone end of the conduit 52, and an outlet 56 b which is located at theother end of the conduit 52. The outlet 56 b is located on a verticallydownward side of the inlet 56 a.

The inlet 56 a of the conduit 52 is connected to the vapor exhaust port46 of the heat receiver 22 via a vapor conduit 58. The outlet 56 b ofthe conduit 52 is directly connected to the coolant inlet 50 of the heatreceiver 22 via a condensed liquid conduit 60, or is connected to thecoolant inlet 50 via a coolant circulation conduit 70 (to be describedlater). The condenser 24 cools the vapor which flows in the conduit 52,condenses the vapor into a coolant liquid, and discharges the coolantliquid from the outlet 56 b to the condensed liquid conduit 60. Thedischarged coolant liquid is returned to the heat receiver 22 throughthe condensed liquid conduit 60.

The condenser 24 may be configured or shaped such that the inside of thecondenser 24 is coated with a paint with high water repellency in orderto promote heat transfer with condensation, and an inclination isprovided make it easier for the generated condensed liquid to flowdownward.

As shown in FIG. 3 and FIG. 4, the radiator 26 includes a plurality ofradiation tubes 62 which extend in the vertical direction and arejuxtaposed in the horizontal direction, an inflow portion 64 a whichcommunicates with lower ends of the radiation tubes 62, an outflowportion 64 b which communicates with upper ends of the radiation tubes62, an inlet 66 a which is provided at the inflow portion 64 a, and anoutlet 66 b which is provided at the outflow portion 64 b. Radiationfins may be provided on peripheries of the radiation tubes 62.

The inlet 66 a of the inflow portion 64 a is connected to the coolantoutlet 48 of the heat receiver 22 via a coolant conduit 68. The inlet 66a is located on a vertically downward side of the coolant outlet 48 ofthe heat receiver 22. The outlet 66 b of the outflow portion 46 b isconnected to the coolant inlet 50 of the heat receiver 22 via thecoolant circulation conduit 70.

If a high-temperature coolant is fed from the heat receiver 22 to theradiator 26 via the coolant conduit 68, the radiator 26 flows thecoolant upward from the inflow portion 64 a through the plural radiationtubes 62 and, during this time, releases the heat of the coolant to theoutside air and cools the coolant via the radiation tubes. Further, theradiator 26 feeds out the cooled coolant to the coolant circulationconduit 70 via the outflow portion 64 b. The discharged coolant isreturned to the heat receiver 22 through the coolant circulation conduit70. In the present embodiment, the condensed liquid conduit 60 isconnected to an intermediate portion of the coolant circulation conduit70. Thereby, the coolant liquid, which has been discharged from thecondenser 24, is fed to the heat receiver 22 via the condensed liquidconduit 60 and coolant circulation conduit 70.

As shown in FIG. 1 to FIG. 3, the air blower 28 is disposed to beopposed to the rear side of the condenser 24 and radiator 26, and theair blower 28 may be configured to be directly attached to the condenser24 and radiator 26, or may be configured to be connected to thecondenser 24 and radiator 26 via an air duct 72. The air blower 28 feedsa cooling wind to the condenser 24 and radiator 26, and facilitatescooling of the condenser 24 and radiator 26. When the air duct 72 isdisposed, the amount of air of the air blower 28 can be increased. Inaddition the condenser 24 and radiator 26 may be configured to bedisposed in a manner to protrude to the outside of the vehicle body,thereby to make use of a traveling wind, which is caused by traveling,as a cooling wind.

The cooling operation of the cooling apparatus 10 having theabove-described structure is described.

As shown in FIG. 3 and FIG. 5, when the semiconductor devices 36 mountedon the heat receiving surface 30 a of the heat receiver 22 are activatedand produce heat, the heat conducts through the heat receiving surface30 a and heats, by heat transfer, the coolant 34 that is sealed in thecontainer body 30 of the heat receiver 22. As the amount of loss in thesemiconductor devices 36 increases, the coolant 34 reaches a saturationtemperature and starts boiling. Bubbles 101, which are generated byboiling, produce a driving force by a difference in density from anambient liquid. Specifically, buoyancy by the bubbles 101 generates anupward stream in the container body 30. With the bubbles 101 rising, theambient coolant 34 also rises accordingly. In the upper part of thecontainer body 30, the coolant 34 has a mixed phase of a gas phase and aliquid phase, that is, a gas/liquid two-phase fluid state.

On the other hand, a vapor 102, which is generated by the heat receiver22, is fed to the condenser 24 via the vapor conduit 58. In thecondenser 24, heat exchange is performed by the radiation fins 54 thatare disposed on the periphery thereof, and the vapor 102 is condensedinto liquid. The condensed liquid of coolant is fed to the lower part ofthe heat receiver 22 via the condensed liquid conduit 60 and coolantcirculation conduit 70.

As shown in FIG. 4 and FIG. 6, at the same time, the high-temperature,gas/liquid two-phase coolant 34 at the upper part of the heat receiver22 flows out of the upper opening 30 b of the container body 30, withthe upward stream thereof becoming a circulation driving stream. Theoutflow coolant 34 is guided to the sub-flow passage 44, and is furtherfed to the inflow portion 64 a of the radiator 26 from the sub-flowpassage 44 via the coolant conduit 68. At this time, the baffle plates42, which are provided at the upper part of the container body 30,prevent the high-temperature coolant from flowing back into the heatreceiver, that is, from flowing back into the neighboring containingchamber 40. Thereby, the coolant, which flows out of the heat receiver22, can efficiently be fed to the coolant conduit 68 via the sub-flowpassage 44.

As shown in FIG. 3, the high-temperature coolant 34, which has flowed inthe radiator 26, flows upward through the radiation tubes 62 and is fedto the outflow portion 64 b, and, during this time, the heat isdissipated and the coolant 34 is cooled. The temperature of the coolant,which flows in from the lower part of the radiator 26, is high, and thetemperature of the upper part within the radiator 26 is relatively low.Thus, by convection due to a difference in density, a heat current movesfrom the lower part to the upper part within the radiation tubes 62 ofthe radiator 26, and the coolant also flows upward. The cooled coolantis fed out to the coolant circulation conduit 70 from the outflowportion 64 b, and is fed to the heat receiver 22 via the coolantcirculation conduit 70.

The condenser 24 and radiator 26 are forcibly air-cooled as one body bycooling air 31 from the air blower 28 which is disposed outside. In thismanner, in the cooling apparatus 10, a natural circulation stream isinduced by the circulation loop structure, without external driving. Ashas been described above, the heat of the semiconductor devices 36 isabsorbed by the heat receiver 22 and coolant 34, and the semiconductordevices 36 are cooled.

According to the natural circulation type cooling apparatus 10 with theabove-described structure, the heat produced from the semiconductordevices 36, which are attached to the heat receiving surface 30 a of theheat receiver 22, is transferred to the coolant 34 within the heatreceiver 22 by heat conduction and heat transfer. When the coolant 34 inthe heat receiver 22 has reached a predetermined saturation temperaturedue to an increase of loss in the semiconductor devices 36, the coolant34 starts boiling. At this time, since the evaporation latent heat, thatis, the latent heat that is removed when the coolant evaporates, isremarkably higher than in the case of usual sensible heat transfer,high-level heat transfer can be performed. By the effect of buoyancy ofbubbles 101 which are generated by the boiling, an upward stream occursand a circulation stream is induced within the apparatus. The generatedvapor 102 is fed to the condenser 24 via the vapor conduit 58, and iscondensed. Thereby, it is possible to suppress an increase in pressurewithin the apparatus due to the generation of vapor, and an increase insaturation temperature value of the coolant 34 due to the increase inpressure, and to maintain a circulation stream of coolant at a desiredtemperature level.

The inside of the cooling apparatus is kept in a reduced-pressure sealedstate, the saturation temperature value of the coolant 34 is lowered,and boiling is started earlier. Thereby, it is possible to satisfy atolerable temperature or below of the semiconductor devices 36.Furthermore, the coolant 34, which has been fed out via the coolantconduit 68, is subjected to heat exchange by the radiator 26, is reducedin temperature, and is circulated once again into the heat receiver 22in a state in which the coolant 34 has a desired subcool degree. Thus,it is also possible to suppress burn-out on the heat conduction surfacewithin the heat receiver 22, and to increase a heat-removal limit value.Thereby, the cooling apparatus can exhibit a good radiation capability.

By disposing the condenser and radiator on the horizontally lateral sideof the heat receiver 22, it is possible to relax restrictions ondisposition of the cooling apparatus and to reduce the size of thecooling apparatus. The inflow portion of the condenser 24 is in ahigh-temperature state due to the vapor. Conversely, the outflow portionof the condenser 24 communicates with the coolant circulation conduitthrough which the coolant cooled by the radiator 26 flows. Hence, apressure difference tends to easily occur between the inlet and outletof the condenser 24, the amount of inflow vapor to the condenser can beincreased, the coolant can efficiently be condensed and circulated, andthe cooling capability can be enhanced. When the flow amount of coolantis small, the heat transfer is promoted within the radiator, and thecirculation of coolant can be stabilized.

From the above, there can be obtained a natural circulation type coolingapparatus, which can relax restrictions on disposition and realizereduction in size, and can exhibit a good heat radiation capability.

Next, natural circulation type cooling apparatuses according to otherembodiments will be described.

In the embodiments to be described below, the structural parts, whichare identical or equivalent to those in the above-described firstembodiment, are denoted by like reference numerals, and a detaileddescription is omitted.

Second Embodiment

FIG. 7 shows a natural circulation type cooling apparatus 10 accordingto a second embodiment.

As shown in FIG. 7, according to the second embodiment, the naturalcirculation type cooling apparatus 10 is configured to adapt to a caseof cooling a plurality of semiconductor devices 36. Specifically, thecooling apparatus 10 includes two heat receivers 22, and the heatreceivers 22 are juxtaposed on the same plane. Semiconductor devices 36are mounted on the heat receiving surface 30 a of each heat receiver 22.The heat receiving surfaces 30 a of the two heat receivers 22 arelocated on the same plane. The condenser 24 and radiator 26 are disposedbetween the two heat receivers 22, and are located on substantially thesame plane as the heat receiving surfaces 30 a of the heat receivers 22.Each heat receiver 22 is connected to the condenser 24 and radiator 26via the vapor conduit 58 and coolant circulation conduit. Two outlets ofthe condenser 24 are connected to coolant circulation conduits viacondensed liquid conduits 60. Specifically, one condenser 24 and oneradiator 26 are provided for the two heat receivers 22. In addition, thecondenser 24 and radiator 26 are handled as one body, and the air blower28 is disposed on the outside, immediately near them, or via an airduct.

In the present embodiment, although not illustrated, such aconfiguration may be adopted that a plurality of cooling apparatuses 10are disposed in parallel, these cooling apparatuses 10 are assembled asone module, and the air blower 28 is disposed on the outside thereof.

In the meantime, the other structure of the cooling apparatus and thestructure of each structural element are identical to those in theabove-described first embodiment.

According to the cooling apparatus 10 with the above-describedstructure, the two heat receivers 22 are disposed on both sides of thecondenser 24 and radiator 26. Thereby, the vapors 102, which are fed outof the heat receivers 22, come together from the two vapor conduits 58and flow in the condenser 24. In addition, the high-temperature coolants34, which flow out of the heat receivers 22, flow in the radiator 26 viatwo condensed liquid conduits 60, and are subjected to heat exchange bythe radiator 26. Thereafter, the coolant 34 in the subcool statebranches into two, and the branched coolants 34 return to the heatreceivers 22 via coolant circulation conduits 70, thus performing acirculation loop operation.

In addition, by disposing the plural cooling apparatuses 10 in parallel,the condenser 24 and radiator 26, which are disposed at the centralpart, can be forcibly air-cooled in the state in which the condenser 24and radiator 26 are integrated as one body. In this case, control isexecuted by varying the output of the air blower 28 in accordance withthe magnitude in amount of radiation heat. The other operations are thesame as in the first embodiment.

According to the cooling apparatus 10 of the second embodiment, onecondenser 24 and one radiator 26 are disposed for two heat receivers 22,and thereby an efficient and good radiation capability can be exhibited.In addition, the volume of the apparatus, that is, the space formounting, relative to the radiation capability of the cooling apparatus,can be reduced. Furthermore, by disposing the plural cooling apparatusesin parallel and blowing the cooling air 31 by the air blower 28, thecooling efficiency of the cooling apparatuses, relative to the number ofsemiconductor devices 36, can be improved, and the size and cost of thecooling apparatus can be reduced. Besides, in the second embodiment,too, the same advantageous effects as with the above-described firstembodiment can be obtained.

Third Embodiment

FIG. 8 is a side view which illustrates a natural circulation typecooling apparatus according to a third embodiment, and FIG. 9 is across-sectional view showing a structure of an upper part of a heatreceiver.

According to the third embodiment, the condenser 24 and radiator 26 ofthe cooling apparatus 10 are disposed on the rear side of the heatreceiver 22, the condenser 24 is disposed on the upper side, and theradiator 26 is disposed under the condenser 24. The air blower 28 forcooling the condenser 24 and radiator 26 is disposed to be opposed tothe condenser 24 and radiator 26, and the air blower 28 air-cools thecondenser 24 and radiator 26 as one body. Although not illustrated, sucha configuration may be adopted that the condenser 24 and radiator 26 arelaterally arranged in parallel, relative to the heat receiving surface30 a of the heat receiver 22 on which the semiconductor devices 36 aremounted, and the condensed liquid, which flows out of the condenser 24,directly flows down into the coolant circulation conduit 70. In thiscase, in order to prevent the subcool coolant 34, which flows out of theradiator 26, from flowing back to the condenser 24, a check vale may bedisposed in the coolant circulation conduit 70.

In the meantime, the other structure of the cooling apparatus and thestructure of each structural element are identical to those in theabove-described first embodiment.

According to the cooling apparatus 10 with the above-describedstructure, the vapor generated by the heat receiver 22 and thehigh-temperature gas/liquid two-phase coolant 34 are fed out,respectively, to the condenser 24 and radiator 26 which are disposed onthe rear side of the heat receiver 22. In this case, as shown in FIG. 9,such a configuration is adopted that when the high-temperaturegas/liquid two-phase coolant 34, which has flowed out of the upperopening of the heat receiver 22, flows from the containing chambers 40which are partitioned by the partition plates 38, the coolant 34 flowsonly a sub-flow passage 44 which faces an opposite surface to the heatreceiving surface 30 a to which the semiconductor devices 36 areattached. Thus, the outflow coolant 34 can easily be caused to flow intothe radiator 26 via the coolant conduit 68.

The air blower 28 for air-cooling the condenser 24 and radiator 26 asone body is disposed on the rear side of the condenser 24 and radiator26. The cooling air 31 is blown not only to the condenser 24 andradiator 26, but also to that surface of the heat receiver 22, which isopposite to the heat receiving surface 30 a to which the semiconductordevices 36 are attached. The operations of the other elements are thesame as in the first embodiment.

According to the cooling apparatus 10 with the above-describedstructure, the condenser 24 and radiator 26 are disposed on the rearside of the heat receiver 22. Thereby, the size of the apparatus in thehorizontal direction, relative to the heat receiving surface 30 a forsemiconductor devices 36 of the heat receiver 22, can be reduced. Inaddition, by making the baffle plates 42 project from the liquid levelin the heat receiver 22, the high-temperature gas/liquid two-phasecoolant 34 is prevented from flowing back to the heat receiver 22, andcan be fed out to the radiator 26 via the coolant conduit 68. Thus,since baffle plates, which are provided at the upper part of the heatreceiver 22, are needless, the local pressure loss within the apparatuscan be reduced, and the circulation efficiency of the coolant 34 can beimproved. Therefore, the apparatus, as a whole, can maintain a desiredradiation capability, and can suppress an increase in pressure withinthe apparatus. Besides, in the third embodiment, too, the sameadvantageous effects as with the above-described first embodiment can beobtained.

Fourth Embodiment

FIG. 10 schematically illustrates a natural circulation type coolingapparatus according to a fourth embodiment. As shown in FIG. 10, in acooling apparatus 10 according to the fourth embodiment, the condenser24 and radiator 26 are disposed on the rear side of the heat receiver22, and the condenser 24 is disposed at the upper part and the radiator26 is disposed at the lower part. The condenser 24 and radiator 26 areprovided on a plane which is perpendicular to the heat receiver 22. Theair blower 28 is disposed to be opposed to the condenser 24 and radiator26 on the rear side of the heat receiver 22, so that cooling air mayflow through both the condenser 24 and radiator 26. In this case, aplurality of cooling apparatuses 10 may be arranged in parallel, so thateach individual condenser 24 and radiator 26 may be air-cooled as onebody by one air blower 28, and the plural individual condensers 24 andradiators 26 may be air-cooled batchwise at the same time.

In the meantime, the other structure of the cooling apparatus and thestructure of each structural element are identical to those in theabove-described first embodiment.

According to the cooling apparatus 10 with the above-describedstructure, the condenser 24 and radiator 26 are air-cooled as one body,and the cooling air 31 by the air blower 28 flows through the condenser24 and radiator 26, and flows in a plane direction which is parallel tothe rear surface of the heat receiver 22 and to the heat receivingsurface 30 a to which the semiconductor devices 36 are attached. In thecase where plural cooling apparatuses 10 are arranged in parallel, thecooling air 31 flows through each condenser 24 and radiator 26.

According to the above-described structure, the same advantageouseffects as with the above-described third embodiment can be obtained,and the cooling air 31 can be flown to the heat receiver 22 from thelateral surface side. Thus, many similar cooling apparatuses can easilybe arranged in parallel on this lateral surface side. In addition, sincemay cooling apparatuses can be cooled batchwise by one air blower 28,the size and weight of the entire apparatus can be reduced. Besides, thesame advantageous effects as with the first embodiment can be obtained.

Fifth Embodiment

FIG. 11 schematically illustrates a natural circulation type coolingapparatus according to a fifth embodiment. As shown in FIG. 11, acooling apparatus 10 according to the fifth embodiment includes two heatreceivers 22 which are disposed to be opposed to each other, and acondenser 24 and a radiator 26 which are provided between the heatreceivers 22, that is, on the rear sides of both heat receivers 22. Thecondenser 24 and radiator 26 are provided on a plane which isperpendicular to the heat receivers 22, and the condenser is 24 isdisposed at the upper part and the radiator 26 is disposed at the lowerpart. In the heat receiver 22, no semiconductor device 36 is mounted onthat surface of the heat receiver 22, which is located on the sidefacing the condenser 24 and radiator 26, that is, on the rear surface ofthe heat receiver 22. Semiconductor devices 36 are mounted on only theheat receiving surface 30 a on the opposite side. The same applies tothe structure of the other heat receiver 22. The air blower 28 isdisposed to be opposed to the condenser 24 and radiator 26.

In the case where many semiconductor devices 36 are mounted and thereare restrictions on disposition in the vertical direction, such aconfiguration is adopted that plural condensers 24 and radiators 26 aredisposed in parallel in the horizontal direction, the air blower 28 isdisposed on the lateral side, and the plural condensers 24 and radiators26 are air-cooled as one body. In the case of the same condition asabove and in the case where there are restrictions on disposition in thehorizontal direction, such a configuration may be adopted that pluralcondensers 24 and radiators 26 are disposed in parallel in the verticaldirection and are air-cooled as one body.

In each of the many cooling apparatuses 10 which are arranged inparallel as described above, vapors 102, which are generated from twoheat receivers 22, are condensed into liquid in the condenser 24 and theliquid flows down to the inlets of the heat receivers 22. In addition,the coolant 34, which has become a high-temperature gas/liquid two-phasefluid in the heat receivers 22, is fed out to the inlet of radiator 26via coolant conduits 68, and is subjected to heat exchange in theradiator. The coolant, which has transitioned into a subcool state bythe lowering in temperature, flows back to both heat receivers 22. Inthe many cooling apparatuses that are arranged in parallel, the airblower 28 is disposed and heat exchange with outside air is performed byforced air-cooling. In the meantime, when there are restrictions ondisposition in the vertical direction, many apparatuses are arranged inthe horizontal direction, the air blower 28 is disposed on the lateralside and caused to blow air, and exhaust air is let to escape to theoutside of the lateral parts of the apparatuses.

According to the cooling apparatus 10 of the fifth embodiment, thecondenser 24 and radiator 26 are disposed on the rear sides of the twoheat receivers 22, that is, the condenser 24 and radiator 26 areinterposed between the two heat receivers 22. Thereby, the apparatussize in the horizontal direction can be reduced. In this structure, evenin the case where there are restrictions on disposition of theapparatus, many apparatuses may be disposed in parallel in thehorizontal direction or vertical direction, and the degree of freedom ofdesign can be enhanced, relative to the increase in number ofsemiconductor devices. In addition, by disposing the air blower 28 onthe lateral surface side or bottom surface side of the condenser 24 andradiator 26, the degree of freedom of disposition of the external airblower can also be enhanced.

In the above structure, not only the condenser 24 and radiator 26 can becooled, but also air can be blown to the heat receivers 22. Thus, thetemperature level in the cooling apparatus can be lowered, and thetolerable temperature of semiconductor devices can further be lowered.Moreover, by setting the coolant 34 in the heat receiver 22 in thesubcool state, the heat-removal limit value can also be increased.Besides, in the fifth embodiment, too, the same advantageous effects aswith the first embodiment can be obtained.

Sixth Embodiment

FIG. 12 schematically illustrates a natural circulation type coolingapparatus according to a sixth embodiment. As shown in FIG. 12, acooling apparatus 10 according to the sixth embodiment includes a heatreceiver 22, a condenser 24 and a radiator 26, which are provided on thesame plane. These components are disposed closer to each other and areconstructed as a unit. In the sixth embodiment, the other structure ofthe cooling apparatus and the structure of each structural element areidentical to those in the above-described first embodiment.

According to the above structure, the same advantageous effects as withthe above-described first embodiment can be obtained, and the size andweight of the apparatus can be reduced by constructing the apparatus asa single unit.

FIG. 13 schematically illustrates a railway vehicle in which a naturalcirculation type cooling apparatus according to a seventh embodiment ismounted. According to this embodiment, a heat receiver 22 of a coolingapparatus 10 is disposed within a housing 21 of a power converter 20which is provided under the floor of the vehicle body 16, and aplurality of semiconductor devices, which are exothermic bodies, aremounted on the heat receiving surface of the heat receiver 22. Acondenser 24 and a radiator 26 of the cooling apparatus 10 are disposedon a horizontally lateral side of the heat receiver 22, on the outsideof the housing 21. The vehicle body 16 includes an air duct 80 forguiding a traveling wind caused by traveling, and the condenser 24 andradiator 26 are disposed in the air duct 80. Thereby, the condenser 24and radiator 26 are cooled as one body by the traveling wind flowing inthe air duct 80. In this case, the air blower 28 may be dispensed with.

The other structure of the cooling apparatus 10 is identical to that ofthe above-described first embodiment. According to the cooling apparatushaving this structure, the same advantageous effects as with the firstembodiment can be obtained. Moreover, the air blower can be dispensedwith, and the manufacturing cost and the space for installation can bereduced.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The exothermic body, which is a target of cooling of the coolingapparatus, is not limited to a semiconductor device of a powerconverter, and may be other exothermic bodies. The material, of whichthe heat receiver and heat receiving surface are formed, is not limitedto the examples in the above-described embodiment, and may be selectedfrom various materials.

What is claimed is:
 1. A natural circulation type cooling apparatuscomprising: a heat receiver comprising a heat receiving surface on whichan exothermic body is mounted, and containing therein a coolant in aliquid phase; a condenser provided on a horizontally lateral side of theheat receiver, and configured to condense a vapor which is generated bythe heat receiver; a radiator disposed on a horizontally lateral side ofthe heat receiver and on a vertically downward side of the condenser,and configured to cool the coolant which is fed from the heat receiverand is heated; a vapor conduit configured to feed the vapor of thecoolant, which is generated by the heat receiver, to an inlet of thecondenser; a condensed liquid conduit configured to feed the coolant,which is condensed, from an outlet of the condenser to a coolant inletof the heat receiver; a coolant conduit configured to feed the coolant,which is heated in the heat receiver, to an inlet of the radiator; and acoolant circulation conduit configured to feed the coolant, which iscooled in the radiator, from an outlet of the radiator to the coolantinlet of the heat receiver.
 2. The natural circulation type coolingapparatus of claim 1, wherein the heat receiver comprises: a containerbody comprising the heat receiving surface and an upper opening, andcontaining the coolant; an upper container configured to cover the upperopening of the container body; a plurality of partition plates providedat intervals within the container body, and configured to partition aninside of the container body into a plurality of containing chamberswhich contain the coolant, respectively; a plurality of baffle platesextending upward from the upper opening of the container body, beyond aliquid level of the coolant, and configured to restrict inflow of thecoolant from each of the containing chambers into another of thecontaining chambers; a vapor outlet formed in the upper container andcommunicating with the plurality of containing chambers via a space inthe upper container; a coolant inlet formed in a lower part of thecontainer body and communicating with the plurality of containingchambers; a coolant outlet formed in the upper container; and a sub-flowpassage defined by the upper container and configured to guide thecoolant, which flows out of the containing chambers, to the coolantoutlet.
 3. The natural circulation type cooling apparatus of claim 2,wherein each of the partition plates comprises an upper end portionwhich extends upward beyond the liquid level of the coolant andconstitutes the baffle plate.
 4. The natural circulation type coolingapparatus of claim 1, wherein the condensed liquid conduit is connectedbetween the outlet of the condenser and an intermediate portion of thecoolant circulation conduit.
 5. The natural circulation type coolingapparatus of claim 1, wherein the radiator comprises an inflow portionwhich includes the inlet of the coolant, an outflow portion whichincludes the outlet of the coolant and is located on a vertically upwardside of the inlet portion, and a plurality of radiation tubes whichextend between the inflow portion and the outflow portion and throughwhich the heated coolant flows.
 6. The natural circulation type coolingapparatus of claim 1, further comprising an air blower configured toblow cooling air to the condenser and the radiator.
 7. The naturalcirculation type cooling apparatus of claim 6, further comprising a ductprovided between the condenser and the radiator, on the one hand, andthe air blower, on the other hand, and configured to guide the coolingair from the air blower to the condenser and the radiator.
 8. Thenatural circulation type cooling apparatus of claim 1, furthercomprising another heat receiver including a heat receiving surface onwhich an exothermic body is mounted, and containing a coolant, whereinthe two heat receivers are arranged such that the heat receivingsurfaces thereof are located in a common plane, and the condenser andthe radiator are disposed between the two heat receivers and aredisposed at lateral side parts of the heat receivers, relative to thecommon plane as the heat receiving surfaces.
 9. The natural circulationtype cooling apparatus of claim 1, wherein the heat receiving surface isformed on one of surfaces of the heat receiver, the condenser isarranged at an upper part on a rear side of the heat receiver, which isopposite to the heat receiving surface, and the radiator is arranged ata lower part on the rear side.
 10. The natural circulation type coolingapparatus of claim 1, wherein the heat receiving surface is formed onone of surfaces of the heat receiver, the condenser is arranged at anupper part on a rear side of the heat receiver, which is opposite to theheat receiving surface, the radiator is arranged at a lower part on therear side, and the condenser and the radiator are provided on a planewhich is perpendicular to the heat receiving surface of the heatreceiver.
 11. The natural circulation type cooling apparatus of claim 1,further comprising another heat receiver including a heat receivingsurface on which an exothermic body is mounted, and containing acoolant, wherein the two heat receivers are arranged such that rearsurfaces thereof, which are opposite to the heat receiving surfaces, areopposed to each other, the condenser is arranged at an upper partbetween the two heat receivers, the radiator is arranged at a lower partbetween the two heat receivers, and the condenser and the radiator arearranged on a plane which is perpendicular to the heat receivingsurfaces of the heat receivers.